The invention is particularly useful in the renewal of large earthmover-type tires by a method wherein the worn lugs and undertread are buffed from the tire casing. U.S. Pat. No. 3,472,714 describes how convolutions of unvulcanized rubber material are then placed around the outer buffed periphery of the tire casing after the lugs and undertread have been removed. Hand-held grooving tools are generally used to form a pattern of grooves in the laminated or spirally wound unvulcanized tread. However, such an operation is time-consuming and costly. Moreover, the appearance of the grooves is dependent on the steadiness with which the operator handles the grooving tool. The invention is directed to providing a machine for automatically cutting grooves into an unvulcanized tread formed on the buffed tire casing.
Briefly stated, the invention is in a machine for grooving the tread of a tire. The machine has a heatable knife for grooving the tread, as well as means for guiding and moving the knife transversely of the tread at a predetermined desired speed. A groove pattern in the form of a cam, having an outer periphery with a desired curvature, is mounted for synchronous rotation with movement of the knife, the rotational speed of the cam being correlated to the speed at which the knife moves transversely of the tread. Means are provided for monitoring the outer curved periphery of the cam and causing correlated movement of the knife guiding means to and from the tread to vary the depth of cut of the knife in accordance with the curvature of the cam being monitored.